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Car always slightly ahead of navigation display...


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  • 2 months later...

I have the same problem, seems like I'm about 300 feet behind on the GPS. That is the only weak point on this unit so far. I have my VSS wire connected and have driven several miles for the learning process. I think Garmin blows this away as far as the GPS, but the VR and the rest of the unit are great.

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  • 4 weeks later...

ive found the original n1 unit to have been the most accurate over the years,

the rest ive sold and installed over the years have all had this annoying little issue

some ahead and most behind

 

it was also the most expensive

probably just a fluke

 

oh well, like others said u will get used to it

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I notice that sometimes I am behind the plotted arrow, and sometimes I am in front of it. Not sure if it is a directional thing, meaning a constant error in one direction/quadrant. In that case, for example, I would always be lagging the plot when headed East, and always be trailing the plot when headed West.

 

This reminds me of the old days before they turned off Selective Availability (SA).

For you young'uns:

 

SA was a technique to reduce the accuracy of unaugmented, single-receiver GPS

measurements. This was accomplished by altering (or "dithering") the GPS

satellite clock signals, and by modifying orbital elements of the broadcast

navigation message. These alterations were done in a coded fashion, and could be

removed by authorized users. This alteration caused horizontal positional errors

on the order of 100 meters (95%), and varied in a manner that prevented rapid

averaging of positional data.

 

BTW, I don't have the reverse signal connected (no BU camera), so I really notice an error after backing out of my garage. The map shows me driving across my neighbor's lawn for a couple of blocks. I'm assuming that the speed sensor and some inertial sensors are using dead reconing for the 30 seconds or so that it takes to get a satellite fix. I guess I should hook-up the reverse sensor. Might as well install the camera too.

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